One day, his father and his family asked him to join them on a picnic but he suddenly disappeared, so they had to go out without him. When they came back at the end of the day, they blamed him for not going out with them. He said, pointing to a book in his hand: “You did not benefit anything from your trip, whereas I memorized all this book in your absence.”
He was known for his physiognomy, sharp memory and wittedness which amazed the people of Damascus and made them admire him more and more. Though he was young, his fame reached the neighbouring territories. Once, one of the scholars of Halab visited Damascus. The scholars and dignitaries of the city went to welcome him. He told them: “I heard in other territories of a boy who is quick in memorizing everything. I came here to see him.”
They led the man to the small school where the boy used to go to memorize the Quran. The Halabi scholar sat for a while until the boy passed with a big board in his hand. The scholar called him, so he went to him.
The scholar took the board from him and said to him: “Sit here son, and I’ll relate to you some Prophetic narrations to write.” He dictated for him some, then he asked him to read them.
The boy started reading from the board. Then the Shaykh said to him: “Let me hear it from you.” He then started recounting the narrations from his memory exactly like he was reading them from the board. The scholar told him: “Erase this, son.” He cited more of the Prophet’s narrations and asked him to repeat them. The boy did the same again; he read it from the board and then from his memory. The scholar stood up saying: “Should this boy live long, he will have a great position [become a great scholar]. We’ve never seen anyone like him before.”
If someone were to recite some verses of the Mighty Qur’an in one of his classes, he would proceed to explain them, and his class would end with this. His class would last for a good portion of the day, and he did not have a designated person to recite for him predetermined
verses that he would prepare for. Rather, any random person who was attending his class would recite what was easy for him, and Ibn Taymiyyah would then explain whatever was recited. He would usually not stop except that those in attendance would know that were it
not for the lack of time, he would have delved into what he was explaining from many, many more angles. However, he would stop in order to allow his listeners to rest.
For example, he delivered a tafsir of “Say, He is Allah, One.’”  that took up an entire huge volume. Also, his tafsir of “The Beneficent ascended the Throne.”  filled around 35 volumes, and I have been told that he began compiling a tafsir that would have taken up fifty volumes had he completed it.
1. surah al-Ikhlas 1 [112:1]
2. surah Ta Ha verse 5 [20:5]
Taken from ‘The lofty virtues of Ibn Taymiyyah’
By The Imam, the Hafidh Abu Hafs ‘Umar bin ‘Ali al-Bazzar
Translated By Abu Sabaayaa
“And from the strangest of things in regards to this is that during his first trial in Egypt, he was taken and jailed, such that he was prevented from having access to his books. During this time, he authored many books – small and large – and mentioned in them what was of ahadith, narrations, statements of the Companions, names of the scholars of Hadith, authors and their works – and he attributed each of these to their proper sources, specifically by name. He also mentioned the names of the books in which each narration was found, as well as where in the books to find them. All of this was purely from his memory, as at the time, he did not have a single book with him to use as a reference. These books were then published and looked over, and – praise be to Allah – not a single mistake was found in any of them, nor did anything need to be changed in them.
And from these books is ‘as-Sarim al-Maslul ‘ala Shatim ar-Rasul,’ and this is from the virtue that Allah – the Exalted – reserved especially for him.”
And to give you an idea of the vastness of the book, the publisher’s introduction goes on to mention that it contains over 250 ahadith, 100 athar, the mention of over 600 famous personalities throughout the history of Ahl as-Sunnah wal-Jama’ah, collected information from over 40 references (and these are just the ones he mentioned by name) – all from memory, and this entire book was written in response to one single incident in which Ibn Taymiyyah heard a Christian insulting the Prophet!